Carbon dioxide(CO_(2))is one of the main factors contributing to the greenhouse effect.The dependence on fossil fuels has led to increasing levels of carbon dioxide in the atmosphere every year.And it is far from enou...Carbon dioxide(CO_(2))is one of the main factors contributing to the greenhouse effect.The dependence on fossil fuels has led to increasing levels of carbon dioxide in the atmosphere every year.And it is far from enough to solve the climate problem by reducing the consumption of fossil fuels to cut down carbon dioxide emissions.In recent years,a series of researches on Carbon Capture,Utilization and Storage(CCUS)have been carried out in various countries around the world.CO_(2) is a nontoxic,tasteless and stable gas at normal temperature.However,when it reaches supercritical state after rising temperature and pressure,it has the characteristics of low viscosity,high diffusivity and high density,and is widely used in green,pollution-free and efficient development technology.Because of these unique properties,supercritical carbon dioxide(sCO_(2))has attracted more and more attention from researchers.sCO_(2) has been widely used in many aspects by virtue of its high solubility and easy compression.Different from previous reviews which only introduced the application of sCO_(2) property,this paper introduces the current research status of the application of the thermodynamic property of carbon dioxide in extraction,dyeing,pharmaceutical,power generation,heat transfer and exploitation of unconventional oil and gas,and mainly analyzes each application in detail from the aspects of working mechanism and improving working efficiency.Finally,the research direction and problems needed to be solved for the application of CO_(2) thermal physics are proposed,which pave the way for other new applications.展开更多
With the advantages of low cost,excellent ability of heat and mass transfer and easy accessibility to the supercritical point,supercritical CO_(2) has been applied in many engineering devices recently.Because of the s...With the advantages of low cost,excellent ability of heat and mass transfer and easy accessibility to the supercritical point,supercritical CO_(2) has been applied in many engineering devices recently.Because of the sharply-varying thermophysical properties near the supercritical point,heat transfer and flow behavior of supercritical CO_(2) in tubes become complex and have received a lot of research attention.The main purpose of this paper is to summarize the findings of the published works related to flow phenomena and heat transfer characteristics of supercritical CO_(2).Firstly,influence parameters related to boundary conditions of supercritical CO_(2) flowing in a smooth tube are introduced.Secondly,commonly-used turbulence and mathematic models dealing with internal flows of supercritical CO_(2) are summarized.Then,research works on geometric effects of design parameters,shapes and configurations are introduced.The practical applications of supercritical CO_(2) in recent years are presented.Finally,developments and future challenges of supercritical CO_(2) in tubes are analyzed and summarized.This paper provides basic knowledge of heat transfer and fluid flow mechanisms and related practical applications of supercritical CO,in tubes.展开更多
Electromagnetic (EM) wave pollution causing damage to precision equipment and threatening thehealth of living organisms has attracted considerable attention. Herein, promising microcellular foamedpolyamide 6 (PA6)/car...Electromagnetic (EM) wave pollution causing damage to precision equipment and threatening thehealth of living organisms has attracted considerable attention. Herein, promising microcellular foamedpolyamide 6 (PA6)/carbon nanotube (CNT) composites for highly efficient EM wave absorption were successfully fabricated using supercritical CO_(2) foaming. Nanocomposites foams with a void fraction rangingfrom 38.7% to 85.1% were achieved, providing a platform to assess the correlation of the electrical conductivity, the dielectric permittivity and the EM wave absorption properties with porosity. Notably, theFoam-257.5C sample with a void fraction of 38.7% exhibited outstanding EM wave absorption characteristics at a thickness of only 1.59 mm and an ultra-low reflection loss value of -55.3 dB (99.9997% wave absorption). Most importantly, the effective absorption bandwidth (EAB) of the Foam-257.5C sample couldcover the entire Ku band (12.4–18 GHz) by slightly adjusting the thickness from 1.20 to 1.60 mm. Thesuperior EM wave absorption performance of the Foam-257.5C sample was attributed to multiple reflections and scattering at the solid-gas interfaces, favorable impedance matching due to the existence ofa large polymer-air interface area, conductive loss near the interfaces and interfacial polarization. Thus,this study offers an eco-friendly, simple and versatile methodology to develop high-efficiency, flexiblepolymer-based EM wave absorbents.展开更多
文摘Carbon dioxide(CO_(2))is one of the main factors contributing to the greenhouse effect.The dependence on fossil fuels has led to increasing levels of carbon dioxide in the atmosphere every year.And it is far from enough to solve the climate problem by reducing the consumption of fossil fuels to cut down carbon dioxide emissions.In recent years,a series of researches on Carbon Capture,Utilization and Storage(CCUS)have been carried out in various countries around the world.CO_(2) is a nontoxic,tasteless and stable gas at normal temperature.However,when it reaches supercritical state after rising temperature and pressure,it has the characteristics of low viscosity,high diffusivity and high density,and is widely used in green,pollution-free and efficient development technology.Because of these unique properties,supercritical carbon dioxide(sCO_(2))has attracted more and more attention from researchers.sCO_(2) has been widely used in many aspects by virtue of its high solubility and easy compression.Different from previous reviews which only introduced the application of sCO_(2) property,this paper introduces the current research status of the application of the thermodynamic property of carbon dioxide in extraction,dyeing,pharmaceutical,power generation,heat transfer and exploitation of unconventional oil and gas,and mainly analyzes each application in detail from the aspects of working mechanism and improving working efficiency.Finally,the research direction and problems needed to be solved for the application of CO_(2) thermal physics are proposed,which pave the way for other new applications.
基金supported by Key Laboratory Continuously Supporting Project(Grant No.WDZC6142703202216)the Natural Science Foundation of Hunan Province(Grant No.2023JJ40733).
文摘With the advantages of low cost,excellent ability of heat and mass transfer and easy accessibility to the supercritical point,supercritical CO_(2) has been applied in many engineering devices recently.Because of the sharply-varying thermophysical properties near the supercritical point,heat transfer and flow behavior of supercritical CO_(2) in tubes become complex and have received a lot of research attention.The main purpose of this paper is to summarize the findings of the published works related to flow phenomena and heat transfer characteristics of supercritical CO_(2).Firstly,influence parameters related to boundary conditions of supercritical CO_(2) flowing in a smooth tube are introduced.Secondly,commonly-used turbulence and mathematic models dealing with internal flows of supercritical CO_(2) are summarized.Then,research works on geometric effects of design parameters,shapes and configurations are introduced.The practical applications of supercritical CO_(2) in recent years are presented.Finally,developments and future challenges of supercritical CO_(2) in tubes are analyzed and summarized.This paper provides basic knowledge of heat transfer and fluid flow mechanisms and related practical applications of supercritical CO,in tubes.
基金This work was funded by the National Key Research and Development Program of China(No.2016YFB0302200)the Key Research and Development Plan of Anhui Province(No.202104g01020003)+2 种基金the Fundamental Research Funds for the Central Universities(No.JKA012011002)the“111 Project”(No.B20031)Also,this research was supported by the China Scholarship Council(No.201906740084)during the work at the University of Toronto.Additional support was provided by Feringa Nobel Prize Scientist Joint Research Center.We would also like to gratefully thank Dr.Biao Zhao for assistance with electromagnetic data analysis in this research.Supplem。
文摘Electromagnetic (EM) wave pollution causing damage to precision equipment and threatening thehealth of living organisms has attracted considerable attention. Herein, promising microcellular foamedpolyamide 6 (PA6)/carbon nanotube (CNT) composites for highly efficient EM wave absorption were successfully fabricated using supercritical CO_(2) foaming. Nanocomposites foams with a void fraction rangingfrom 38.7% to 85.1% were achieved, providing a platform to assess the correlation of the electrical conductivity, the dielectric permittivity and the EM wave absorption properties with porosity. Notably, theFoam-257.5C sample with a void fraction of 38.7% exhibited outstanding EM wave absorption characteristics at a thickness of only 1.59 mm and an ultra-low reflection loss value of -55.3 dB (99.9997% wave absorption). Most importantly, the effective absorption bandwidth (EAB) of the Foam-257.5C sample couldcover the entire Ku band (12.4–18 GHz) by slightly adjusting the thickness from 1.20 to 1.60 mm. Thesuperior EM wave absorption performance of the Foam-257.5C sample was attributed to multiple reflections and scattering at the solid-gas interfaces, favorable impedance matching due to the existence ofa large polymer-air interface area, conductive loss near the interfaces and interfacial polarization. Thus,this study offers an eco-friendly, simple and versatile methodology to develop high-efficiency, flexiblepolymer-based EM wave absorbents.